Research is proposed to design and demonstrate an industrial ventilation system for portable welding and grinding and to develop a computer aided design program that can be used by engineers to design similar ventilation systems. The computational procedure will enable designers to compute air velocities, particle trajectories, and contaminant concentrations in the region between the contaminant source and a hood configuration of his choosing. The program will be written so that the designer can easily change the hood configuration to recalculate the above and assess how changes in the design affect the hood's performance. The program provides designers a capability they presently do not have, the ability to quickly and quantitatively assess the affects of changing the hood configuration and exhaust flow rate.